In this competitive renewal, five principal investigators, who have a strong track record in making novel contributions to angiogenesis research, propose to continue their collaborative efforts by studying novel activities of a set of endogenous molecules and structures that regulate angiogenesis by previously unknown mechanisms. J. Folkman (Project I) will elucidate new mechanisms by which specific endogenous angiogenesis regulatory proteins (e.g., thrombospondin-1 and endostatin) found in platelets, and in stromal cells and their extracellular matrix, suppress pathological angiogenesis, and oppose the tumorigenic activity of activated oncogenes. M. Klagsbrun (Project II) will study new angiogenesis regulatory functions of two proteins, neuropilin and semaphorin, that were previously thought to exclusively regulate neuronal growth and migration. D. Ingber (Project III) will investigate how physical interactions between cells and extracellular matrix regulate the small GTPases Rho and Rac, and thereby govern directional migration of capillary cells during tumor angiogenesis in vitro and in vivo. Patricia D'Amore (Project IV) will examine the potential antiadhesive function of endomucin, a down stream target of VEGF, in vascular lumen formation. Marsha Moses (Project V) will analyze the mechanism by which the metalloproteinase ADAM12 regulates angiogenesis, as well as tumor growth and metastasis. She will also determine whether ADAM 12 may be used as an early biomarker of recurrent cancer, disease status or efficacy of therapy in cancer patients. Together, the five research programs in this application cover a broad range of investigation that should significantly enhance our understanding of how angiogenesis is regulated. The results of these experiments are likely to provide a broader spectrum of targets for antiangiogenic therapy, and lead to the development of new diagnostic and prognostic biomarkers. Summary: The body has a variety of defenses against cancer. One of the strongest defenses consists of special proteins that prevent early tumors smaller than a pinhead from recruiting new blood vessels. These are called endogenous angiogenesis inhibitors. Many of them were first discovered by the five principal investigators who are working together on this Program Project. These investigators will now study the different mechanisms by which a set of these proteins operate to prevent tumor angiogenesis. The expected result from this body of work should be the possibility of new angiogenesis inhibitors for which there would be less risk of the development of resistance by a tumor, and the possibility of developing blood tests and urine tests that could detect recurrent cancer long before symptoms appear, or before a tumor can be seen by current methods.